Evolutionary biologist Paul Ewald drags us into the sewer to discuss germs. Why are some more harmful than others? How could we make the harmful ones benign? Searching for answers, he examines a disgusting, fascinating case: diarrhea.

After years of studying illness from the germs' point of view, microbiologist Paul Ewald believes that Big Pharma is wrong about some very big issues. What's right? The leader in evolutionary medicine posits radical new approaches.
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